Phosphorus-copper base brazing alloy

ABSTRACT

A solid phos-copper base brazing alloy component for forming a brazed joint with a raised shoulder and little to no black oxide. The brazing alloys of the present invention are visually distinguishable from copper and copper alloy parts and may provide a good color match for silver and silver alloys, including sterling silver. The solid brazing components of the present invention may be used in forming brazed joints at low brazing temperatures and result in a joint that is ductile, smooth and corrosion resistant. The solid brazing components are provided in the form of wire, strip, foil or a preform, and thus are advantageously used in a wide variety of brazing applications including copper tubing and intricate jewelry. The brazing components of the present invention are made of an alloy having a liquidus temperature above 840° F. and consist essentially of about 4-10% phosphorus, about 0.1-8% tin, up to about 4% antimony, about 0.001-3% silicon, up to about 18% silver, up to about 3% nickel, up to about 3% manganese, with the balance being copper. Exemplary embodiments include about 0.1-18% silver and/or 0.1-3% nickel.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of co-pending U.S. patent application Ser. No. 10/086,121, filed Feb. 27, 2002, which is a continuation-in-part of co-pending U.S. patent application Ser. No. 10/027,090, filed Dec. 20, 2001, which is a continuation-in-part of U.S. patent application Ser. No. 09/913,000, filed Jul. 25, 2001.

FIELD OF THE INVENTION

[0002] This invention relates to a solid copper brazing component and method for forming a brazed joint, and in particular, a brazing component for joining copper, copper alloys, silver and silver alloys.

BACKGROUND OF THE INVENTION

[0003] Copper and copper alloys have been brazed successfully for many years with metals comprising the phosphorus-copper alloys, also known as phos-copper alloys. Silver is often added to the base metals to accomplish special features for a wide variety of applications. These alloys are generally known as silver-phos-copper alloys. Silver brazing alloys, composed primarily of silver, copper, zinc, tin, nickel, manganese, and cadmium, are used to braze ferrous and non-ferrous metals and alloys. These silver brazing alloys are designed to work at low temperatures and to provide strong, ductile joints.

[0004] Additions of other elements, such as tin, antimony, nickel or silver, to phos-copper and silver-phos-copper alloys have been made in an effort to lower the melting range temperatures or to reduce the phosphorus content to increase ductility. For example, U.S. Pat. No. 5,066,456 discloses that the addition of tin and antimony up to six percent each to a phos-copper based alloy lowers brazing temperatures.

[0005] Air conditioning coils, heat exchangers, water coolers and other copper coils are manufactured by connecting copper tubing and fittings by brazing with phos-copper or silver-phos-copper brazing alloys. These alloys produce strong, ductile brazes, but the industry has long experienced a relatively high percentage of leaks after brazing, particularly with BCuP-2 alloys. Most leaks are caught on the production floor during testing and are repaired. This double work of brazing and testing is very costly. More damaging, very tiny leaks can evade factory testing and end up as warranty work in the field, which is both expensive and damaging to the company's brand image.

[0006] The phos-copper alloys now on the market all range within a solidus temperature of 1310° F. to a liquidus temperature of 1500° F. Alloys of even higher phosphorus content, up to 8%, are now in use to enhance productivity because of their lower operating temperature cost considerations. The non-silver alloys in this group are the most commonly used in industry and contain 7% to 7.4% phosphorus, the balance being copper. The fact that these phos-copper alloys flow and join very well is problematic in that they also flow very thinly. Torch and furnace brazing is performed as rapidly as possible to achieve good productivity. While these alloys are quick to braze, they are difficult to observe for soundness. The entire 360° of the brazed joint must be carefully viewed by the operator, for it is here that a correction, if needed, should be made. These thin-flowing alloys produce only a very small cap, or shoulder, around the pipe at the fitting junction. The alloys are thin-flowing in that they flow like a heavy coating of paint, instead of more thickly as in a putty used to seal a ⅛″ crack.

[0007] Even a skilled brazer cannot tell 100% of the time that he has a totally leak-free connection by visually looking at his completed braze. In some places on a given braze connection, the brazing alloy can be seen to be in place as a shoulder between the two parts, while in other places the alloy drops in the adjoining area (the capillary) without forming any noticeable shoulder. When viewing this very closely, the operator can often see that the joint appears to be 100% sound, but he can't be certain of it. Most air conditioning companies submerge each copper coil, which comprises perhaps 100 brazes, into a water tank, and air pressure is added to this coil to determine if there are any leaks. Wherever leaks are found, brazing must be repeated.

[0008] The now-in-use phos-copper alloys, as described above, could be modified to form an advantageous cap by lowering the phosphorus content significantly. However, doing so is not feasible because the liquidus temperature rises to a point of endangering the copper being brazed. It is noteworthy that silver in the range of 6-15%, when added to the phos-copper alloys described above, lowers the solidus temperature to 1190° F., allows the phosphorus contents to be reduced as much as 2%, allows the alloy to flow in a much thicker manner, and effects a noticeable cap or shoulder to the brazed area. The popular 15% silver-phos-copper alloy has the consistency of hot taffy when hot enough to braze, and easily forms a large cap or shoulder at the joint area. This visible fillet is quickly seen by the operator and any omission in the braze can be remedied. However, the addition of silver is quite expensive.

[0009] Another serious deterrent to being able to observe the quality of copper tubing brazed with phos-copper or silver-phos-copper brazing alloys is the formation of a black oxide that is formed on the actual braze surface and on the adjacent copper pipe. Because the braze and the copper pipe all turn black, it is difficult to closely inspect the actual braze.

[0010] There is thus a need for a phos-copper base alloy system that brazes at low temperatures, forms a noticeable cap or shoulder to facilitate visual inspection, and does not form black oxide to any extent that will obscure visual inspection.

SUMMARY OF THE INVENTION

[0011] The present invention provides a solid phos-copper base brazing alloy component suitable for forming a brazed joint with a raised shoulder and little to no black oxide, that is visually distinguishable from copper or copper alloy parts and/or provides a good color match for silver and silver alloys. The brazing filler metal of the present invention incorporates an advantageously low brazing temperature range and is both ductile, smooth and corrosion resistant. The brazing alloys of the present invention can be easily fabricated into wire, strip, foil and various ring and strip preforms, thereby providing a solid brazing component suitable for numerous brazing applications, such as brazing large copper pipe fittings. To this end, a solid brazing component is provided in the form of wire, strip, foil or a preform. The component is made of an alloy having a liquidus temperature above 840° F. and which consists essentially of about 4% to about 10% phosphorus; about 0.1% to about 8% tin; about 0.001% to about 3% silicon; up to about 18% silver; up to about 3% nickel; up to about 4% antimony; up to about 3% manganese, and the balance copper. In exemplary embodiments, the alloy includes about 0.1% to about 18% silver and/or about 0.1% to about 3% nickel.

[0012] The present invention further provides a method for forming a brazed joint in which the brazing component described above is placed between two metal parts, such as copper tubing or sterling silver parts, the component is heated to a temperature to melt at least a major portion of the brazing alloy, thereby causing it to wet and flow between the parts, and then the alloy is cooled. The brazing component of the present invention produces a substantial raised shoulder or cap about the brazed joint, which is a visible sign to the operator that the joint is sound.

[0013] The brazing component of the present invention further produces a brazed joint with little to no black oxide that can obscure the operator's view of the soundness of the joint. In addition, the combination of alloying elements significantly reduces the melting range of these brazing filler metals, thereby providing a cost savings by reducing the use of expensive fuel gases and the time required of the brazing process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the Office upon request and payment of the necessary fee.

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

[0016]FIGS. 1 and 2 are photographs of brazed copper joints wherein the copper tubing on the left has been brazed with a phos-copper alloy (BCuP-2) of the prior art, and the copper tubing on the right has been brazed with an alloy of the present invention.

[0017]FIGS. 3 and 4 are photographs of the front and back, respectively, of a copper plate brazed to a brass plate with an alloy of the present invention.

[0018]FIG. 5 is a photograph of a 1 inch copper pipe brazed with a silver-phos-copper alloy (BCuP-5) of the prior art with 2% nickel and 0.02% silicon additions.

[0019]FIG. 6 is a photograph of a 1 inch copper tube brazed with a silver-phos-copper alloy of the present invention having 2% nickel, 0.02% silicon and 6.7% tin additions.

[0020]FIG. 7 is a photograph of a sterling silver plate brazed with a phos-copper alloy of the present invention, demonstrating the substantial color match between the sterling silver and the brazed alloy.

DETAILED DESCRIPTION

[0021] The present invention provides phos-copper base brazing alloys that are materially improved in their properties by the addition of specified amounts of tin and silicon, and further by specified additions of nickel and/or silver. The melting range can be lowered, narrowed or broadened. In other words, the specified alloy additions lower one or more of the liquidus, major thermal arrest (MTA) or solidus temperatures. As used herein, the liquidus temperature refers to that temperature at which the alloy is completely liquid, i.e. at which the alloy finishes melting upon heating. The solidus temperature refers to that temperature at which a metal is completely solid, i.e., at which the alloy begins to melt upon heating. Thus, the brazing temperature range extends from the solidus temperature to the liquidus temperature. The brazing temperature, or melting temperature at which the alloy wets and flows, is generally considered to be between the solidus and liquidus temperatures. Some alloys exhibit thermal arrests between the solidus and liquidus, which may be observed on the cooling curve for a given alloy, with the major thermal arrest (MTA) temperature indicating the melting temperature of a major portion of the alloy. For alloys that do exhibit a MTA, the brazing temperature is generally considered to be at or near the MTA. For alloys that do not exhibit a MTA, the brazing temperature (i.e., temperature at which a major portion of the alloy is melted) is generally considered to be at or near the liquidus temperature.

[0022] The alloys of the present invention form a large cap, or shoulder, during the brazing process that is clearly visible, and they do so at a brazing temperature that has not been possible with phos-copper brazing alloys in the past without the addition of silver to the composition of the alloys. In fact, the phos-copper base alloys of the present invention which include tin and silicon, and advantageously nickel, will form a cap or shoulder similar to or superior to silver-phos-copper alloys of the prior art, and will do so at lower brazing temperatures than the prior art silver-containing alloys. The phos-copper base alloys of the present invention which include silver, tin and silicon, and advantageously nickel, also form a cap or shoulder similar to or superior to silver-phos-copper alloys of the prior art and will do so at significantly lower brazing temperatures than the prior art silver-containing alloys, particularly for high silver contents, such as 6-18%. The liquidus and MTA temperatures of brazing alloys of the present invention more closely represent the most important characteristic of where the alloy flows (the working temperature). The filler metal can readily fill loose connections and cap large copper fittings. Specific formulations of this alloy can accommodate near-eutectic melting characteristics to braze tight-fitting parts and conversely, to fill loose connections as large as 0.050″.

[0023] The large caps formed by brazing with the phos-copper base alloy compositions of the present invention (without silver addition) are a bright tin or silver color, and their presence is easily seen. This is an advantage over the phos-copper alloys of the prior art that do not cap well and are black in color after brazing. The brazing torch operator has great difficulty viewing the previous copper brazes because the braze itself is black from oxide as is the copper adjacent to the braze. This can contribute to leaks in the manufacturing of such components as air conditioning copper coils, leaks that can be avoided by the operator's being able to see a bright metal braze (cap or seal) that is contiguous and complete. The phosphorus-tin-silicon-copper alloys and the phosphorus-tin-nickel-silicon-copper alloys of the present invention cause no blackening on the braze or on the adjacent copper.

[0024] To this end, a solid brazing component is provided as a wire, strip, foil or preform, wherein the brazing component has a liquidus temperature above 840° F., thus making the component suitable for brazing techniques. The brazing component is made of an alloy consisting essentially of, in weight percent, about 4-10% phosphorus, about 0.1-8% tin, and about 0.001-3% silicon. In all alloy examples provided herein, the balance of the composition is copper. Further, in all alloys described herein, all or a portion of the tin may be replaced by antimony, which serves the same or similar function in the alloy, but preferably the antimony content does not exceed about 4%, and the sum of tin and antimony does not exceed about 10% of the alloy composition. The alloys of the present invention may further include up to about 3% nickel, and advantageously include nickel in an amount of about 0.1-3%. In another exemplary embodiment of the present invention, the alloys may further include up to 18% silver, and advantageously contain silver in an amount of about 0.1-18%. In yet another exemplary embodiment of the present invention, the alloy includes both silver and nickel additions. All alloys of the present invention may further include up to about 3% manganese without departing from the scope of the present invention. Manganese is a known alloying addition for increasing the toughness and hardness of the brazing alloy. Further, alloys including impurity amounts of other elements are considered within the scope of the present invention. Impurities may be present by virtue of the raw materials used to make the alloys, and are to be distinguished from elements intentionally added to the alloy melt for the purpose of affecting the properties of the alloy.

[0025] As may be appreciated by one skilled in the art, variations in the amounts of each of the alloying elements, within the above-described ranges, will have an effect on the liquidus, MTA and solidus temperatures of the brazing alloy. The following alloys are provided as exemplary, in that they achieve a reduction in the liquidus, MTA, and/or solidus temperatures, form a substantial cap or shoulder, and produce little to no blackening on the braze or adjacent metal. In no way should the following recitations be considered to limit the scope of the present invention to the specific exemplary alloys. A first exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 4-10% phosphorus; (b) about 6-8% tin; (c) about 0.001-3% silicon; (d) about 1.4-2% nickel, and the balance copper. These alloys generally exhibit narrow melting ranges, such as on the order of about 1090° F. to about 1280° F., and MTA's at about 1215-1240° F. Optional additional elements may include up to 4% antimony, up to 18% silver and up to 3% manganese.

[0026] A second exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 5-10% phosphorus; (b) about 0.1-6% tin; (c) about 0.001-1% silicon, and the balance copper. An alloy of this embodiment may exhibit an even more narrow melting range, such as on the order of about 1285° F. to about 1390° F., or with a 2% nickel addition, a broad melting range, such as on the order of about 1100° F. to about 1460° F. and a MTA of about 1225-1255° F. Optional additional elements may include up to 2% antimony, up to 18% silver, up to 3% nickel and up to 3% manganese.

[0027] A third exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 6-7% phosphorus; (b) about 2-8% tin; (c) about 0.001-1% silicon, and the balance copper. These alloys all exhibit a lower liquidus temperature than BCuP-2 alloys of the prior art, and certain alloys exhibit a MTA that is more than 200° lower than the liquidus temperature for BCuP-2. Optional additional elements may include up to 2% antimony, up to 18% silver, up to 3% nickel and up to 3% manganese.

[0028] A fourth exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 6% phosphorus; (b) about 6-7% tin; (c) about 0.02% silicon; (d) about 6-10% silver, and the balance copper. These alloys generally exhibit a lower solidus temperature, a lower liquidus temperature, and a lower MTA than BCuP-4 and BCuP-5 alloys of the prior art. Optional additional elements may include up to 2% antimony, up to 3% nickel and up to 3% manganese.

[0029] A fifth exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 5-6% phosphorus; (b) about 6-7% tin; (c) about 0.02% silicon; (d) about 2% nickel; (e) about 15% silver, and the balance copper. These alloys may exhibit a solidus temperature on the order of 1030° F. and a liquidus temperature on the order of about 1260° F. or less. Optional additional elements may include up to 2% antimony and up to 3% manganese.

[0030] A sixth exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 6-7% phosphorus; (b) about 2-7% tin; (c) about 0.01-0.1% silicon; (d) about 3% silver, and the balance copper. These alloys generally exhibit a low, narrow melting range. Optional additional elements may include up to 2% antimony, up to 3% nickel and up to 3% manganese.

[0031] A seventh exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 6-7% phosphorus; (b) about 6-7% tin; (c) about 0.01-0.1% silicon; (d) about 1-2% nickel, and the balance copper. These alloys generally exhibit liquidus or MTA temperatures on the order of 1215-1255° F. Optional additional elements may include up to 2% antimony, up to 18% silver and up to 3% manganese.

[0032] An eighth exemplary embodiment of a brazing component of the present invention is made of an alloy consisting essentially of, in weight percent: (a) about 4-7% phosphorus; (b) about 5-7% tin; (c) about 0.01-0.1% silicon; (d) about 1.4-2% nickel; (e) about 5-18% silver, and the balance copper. These alloys generally exhibit a solidus temperature of 1060° F. or less and liquidus or MTA temperatures on the order of 1105-1160° F. Optional additional elements may include up to 2% antimony and up to 3% manganese.

[0033] Exemplary alloys of the present invention exhibit a liquidus temperature less than about 1300° F. and a solidus temperature less than about 1200° F. Other exemplary embodiments exhibit a liquidus temperature less than about 1300° F. and a solidus temperature less than about 1100° F. In general, for those alloys with a narrow brazing temperature range, such as less than 150°, no MTA is present. In these embodiments, brazing may thus be performed at temperatures below 1400° F., and advantageously below 1300° F., and even below 1130° F. for some silver-containing embodiments. For those alloys having a broader brazing temperature range, an MTA is present which is generally on the order of about 1125-1255° F., such that brazing may be performed at temperatures below 1255° F.

[0034] A joint is brazed in accordance with the present invention by placing a solid brazing component having one of the compositions described above between two metal parts, heating the solid brazing component to melt at least a major portion of the alloy (i.e., heating to a brazing temperature at or near the MTA or liquidus temperature) to cause the alloy to wet and flow between the two metal parts, then cooling the alloy to form the brazed joint, whereby a raised cap is visible between the two metal parts, and the joint and adjacent metal parts are substantially free of black metal oxide. In one embodiment, the metal parts may be two copper or copper alloy parts and the brazed joint will be visually distinguishable from the parts, preferably having a bright tin or silver color. Alternatively, the metal parts may be sterling silver and the brazed joint is substantially the same color as the sterling silver. The solid brazing components of the present invention are suitable for brazing a wide variety of parts of both simple and intricate shapes. For example, the brazing components are suitable for brazing tubular shaped parts, whereas powder brazing alloys of the prior art are not easily used in that environment. Additionally, small, intricate pieces of silver jewelry may be brazed with the solid brazing components of the present invention. In an exemplary embodiment of the method of the present invention, the solid brazing component is heated to a temperature less than 1400° F., by virtue of the alloy having a liquidus and/or MTA temperature below 1400° F. In a further exemplary embodiment of the present invention, the solid brazing component is heated to a temperature less than 1300° F., by virtue of the alloy having a liquidus and/or MTA temperature below 1300° F.

[0035] The alloys of the present invention, in their broadest form, consist essentially of at least copper, phosphorus, tin (or antimony) and silicon. Silicon, in combination with tin, achieves benefits to a degree not obtainable by the addition of either element alone to the phos-copper base alloys. Compared to Cu—P alloys of the prior art, Cu—P—Sn—Si alloys of the present invention exhibit lower liquidus, MTA and/or solidus temperatures, thereby allowing brazing to take place within a lower temperature range. Silicon addition to these alloys also creates the advantage of lowering the surface tension when they are in the molten state. This allows the brazing alloys to better penetrate tightly fitting parts and to achieve fuller coverage of the surfaces to be brazed. For example, leaks in copper coils used in air conditioning systems are often caused by small voids within a braze, connecting with one another, to form a path wherein refrigerant gases escape.

[0036] Silicon additions in the presence of tin also offer the advantage of changing the color and texture of phos-copper base brazes from a dull, grainy, brown finish to a very smooth finish of bright tin or silver color. To achieve this color and texture change, these alloys require a tin or antimony content of not less than 0.1% and not greater than 10% individually or in combination. In particular, when added in the presence of tin (0.1% to 8.0%) and/or antimony (up to 4.0%), a color change is effected to a bright tin or silver color finish after brazing. Silicon addition also increases the average tensile strength of phos-copper alloys.

[0037] Nickel, in combination with tin and silicon, in the phos-copper base alloys, is also responsible for lowering the melting range of the brazing alloy, increasing the hardness, increasing corrosion-resistance, and smoothing the surface of the finished braze area. By way of example, an alloy of the present invention consisting essentially of 6% phosphorus, 6% tin, 15% silver, 2% nickel and 0.02% silicon, balance copper, tests to a Rockwell B hardness of 87, whereas the BCuP-5 alloy of the prior art (alloy 14 in Table 2, below) tests to a lower Rockwell B hardness of only 81. The resultant brazes from alloys of the present invention are also ductile and strong. Several destructive tests on copper brazes made with Cu—P—Sn—Ni—Si alloys of the present invention conducted by the Edison Welding Institute resulted in failure of the base metal, rather than the brazed joint.

[0038] Cooling curves run on a phos-copper BCuP-2 braze alloy (alloy 1) of the prior art and phos-copper base alloys of the present invention containing tin and silicon additions or containing tin, nickel and silicon additions are analyzed and the results set forth in Table 1, showing solidus, MTA and liquidus temperatures. Minor thermal arrests often appear in the cooling curves but are not shown. All values are percents by weight. TABLE 1 Liqui- Soli- dus MTA dus Alloy % Cu % P % Sn % Ni % Si % Sb ° F. ° F. ° F.  1* 92.9 7.1 — — — — 1475 — 1310 2 89.28 6.7 2 2 0.02 — 1460 1253 1110 3 86.28 6.7 5 2 0.02 — 1344 1229 1102 4 90.15 6.75 2 — 0.1 1 1389 — 1285 5 85.68 6.7 6.6 1 0.02 — 1253 — 1237 6 85.28 6.7 6.6 1.4 0.02 — 1269 1239 1090 7 84.88 6.7 6.6 1.8 0.02 — 1279 1223 1093 8 84.68 6.7 6.6 2 0.02 — 1280 1215 1090

[0039] Table 1 illustrates significant reductions in temperature across the melting range of the phos-copper base alloys of the present invention as compared with the BCuP-2 brazing alloy (alloy 1) of the prior art. Brazing temperatures for the tin, nickel, silicon phos-copper alloys are lower than the phos-copper BCuP-2 brazing alloys, even when modified with higher phosphorus. The substantial reduction of required brazing temperatures effects considerable savings of both fuel gases and cycle time of brazing operations. The lower brazing temperatures also lessen the degree of annealing caused to parent copper and brass metals with the phos-copper base alloys. Such annealing causes the metal to soften and to become very weak. Also, in some very hot brazing furnaces, slight melting of the copper or brass base parts can occur.

[0040] A comparison of alloys 2, 3 and 4 of the present invention with the BCuP-2 alloy (alloy 1) of the prior art demonstrates the synergistic effect achieved by the addition of silicon, tin and nickel in accordance with the present invention. The BCuP-2 alloy does not exhibit a MTA, and so brazing occurs at or near the liquidus temperature of 1475° F. Addition of 2% tin and 1% antimony, in combination with 0.1% silicon, and a reduction in the phosphorus content, as in alloy 4, achieves a lowering of both the solidus and liquidus temperatures compared to the BCuP-2 alloy, and brazing occurs at or near the liquidus temperature of 1389° F. Decreasing the silicon content to 0.02 and adding 2% nickel, as with alloy 2, increases the liquidus temperature, substantially reduces the solidus temperature, and produces a MTA at 1253° F., whereby brazing will occur at or near 1253° F. Increasing the tin content to 5%, as in alloy 3, maintains the low solidus temperature achieved by the nickel addition, and lowers the liquidus and MTA temperatures to 1344° F. and 1229° F., respectively, and brazing will occur at or near 1229° F. Thus, by optimizing the nickel, tin and silicon contents, significant changes can be made to occur in the liquidus, MTA and solidus temperatures, and brazing can occur at substantially lower temperatures. With respect to alloys 5-8, a further increase in tin to 6.6% further reduces the liquidus temperature to 1280° F. or less. Alloy 5 exhibits a very narrow melting range. Keeping the phosphorus, tin and silicon contents constant, and varying the nickel content between 1% and 2% demonstrates that the low liquidus temperature is maintained, while a significant decrease in solidus temperature is obtained with nickel quantities ranging from about 1.4%-2%.

[0041]FIGS. 1 and 2 show on the left a copper joint that has been brazed with a BCuP-2 phos-copper alloy (alloy 1) of the prior art, available commercially from J. W. Harris Co., Inc. (Mason, Ohio) under product name “Harris 0.” There is an absence of any substantial shoulder about the brazed joint, and there is substantial black oxide about the joint and adjacent copper tubing, which obscures the operator's view of the soundness of the joint.

[0042]FIGS. 1 and 2 show on the right a copper joint that has been brazed with an alloy of the present invention, specifically a Cu-6.7P-6.65Sn-0.015Si alloy. A substantial cap or shoulder is present, and, in addition, there is little or no black oxide present. Moreover, the brazed joint has a smooth, bright, tin-colored appearance that is visually distinguishable from the adjacent copper tubing, whereby visual inspection can detect whether the braze is contiguous and complete.

[0043]FIGS. 3 and 4 depict a 0.05 inch copper plate brazed to a 0.05 inch brass plate using the same Cu-6.7P-6.65Sn-0.015Si alloy as used in FIGS. 1 and 2. FIG. 3 is a front view of the brazed plates, further including a copper return bend tube brazed to the brass plate. The braze has a bright tin/silver-colored appearance that is highly visually distinguishable from the adjacent copper and brass plates and between the return bend and the brass plate. FIG. 4 is a back view of the brazed plates, illustrating that the alloy of the present invention flowed through the joint to form a complete and contiguous braze that may be visually inspected from both the front and back of the plates. No black oxide is present at the brazed joints.

[0044] Table 2 illustrates examples of phos-copper base alloys similar to those of Table 1, but including silver addition. In other words, Table 2 is directed to silver-phos-copper alloys of the present invention. Table 2 also includes the BCuP-4 (alloy 12) and BCuP-5 (alloy 14) alloys of the prior art for comparison purposes. All values are percents by weight. TABLE 2 Liquidus MTA Solidus Alloy % Cu % P % Ag % Sn % Ni % Si % Sb ° F. ° F. ° F.  9 86.15 6.75 3 2 — 0.1 2 1296 — 1238 10 82.58 6.7 3 6.2 1.5 0.02 — 1226 1201 1033 11 86.98 7 2 2 2 0.02 — 1458 1246 1128  12** 86.80 7.2 6 — — — — 1335 1246 1190 13 79.98 6 6 6 2 0.02 — 1288 1160 1060   14*** 80.00 5 15 — — — — 1480 1194 1190 15 71.98 5 15 6 2 0.02 — 1260 1127 1030 16 70.28 6 15 6.7 2 0.02 — 1107 — 1028 17 67.98 6 18 6 2 0.02 — 1118 — 1028

[0045] A reduction in brazing temperature is generally apparent in the silver-phos-copper alloys containing tin and silicon, in particular those further containing nickel, and more in particular for those alloys containing about 5-18% silver. Alloy 9 exhibits a lower liquidus temperature than the BCuP-4 alloy (alloy 12), and a very narrow melting range. Alloys 10-11 in comparison to the BCuP-4 alloy (alloy 12) demonstrate that even with lower silver content, the addition of tin, nickel and silicon maintains or lowers the MTA temperature and decreases the solidus temperature of the brazing alloy. Alloy 11 further demonstrates a substantial decrease in the liquidus temperature upon increasing the tin content. A drastic reduction in the solidus, MTA and liquidus temperatures is achieved by increasing the silver and tin contents, as in alloys 13 and 15-17. In each of these alloys, the liquidus temperature is below 1300° F. and the solidus temperature is below 1100° F. Alloys 13 and 15 exhibit lower MTA temperatures. It may also be observed that a very low and narrow melting range is provided in alloys 16 and 17, which contain about 6% phosphorus, 15-18% silver, 6-7% tin, 2% nickel and 0.02% silicon.

[0046]FIGS. 5 and 6 visually demonstrate the synergistic effect of tin and nickel in the silver-phos-copper alloys. FIG. 5 depicts a 1 inch copper pipe that has been brazed with the BCuP-5 alloy (alloy 14) modified with a 2% nickel and 0.02% silicon addition, i.e., Cu-5P-15Ag-2Ni-0.02Si. The brazed joint is rough and porous, such that this alloy is not considered suitable for brazing. FIG. 6 depicts a 1 inch copper pipe brazed with alloy 16 in Table 2, i.e., Cu-6P-6.7Sn-15Ag-0.02Si-2Ni. The brazed joint is smooth and solid and is easily visually distinguished from the adjacent copper pipe, with a large cap and shiny appearance that is not obscured by black oxide. FIGS. 5 and 6 demonstrate that nickel may be added to the phos-copper base alloys when accompanied by tin to provide an alloy suitable for brazing that forms a smooth, solid visually distinguishable brazed joint. As silicon and nickel are added, in the presence of tin (0.1% to 8.0%) and/or antimony (up to 4.0%), a color change is effected to a bright silver color finish after brazing.

[0047]FIG. 7 is a photograph of a sterling silver plate on which an alloy of the present invention has been brazed, specifically alloy 8 in Table 1 consisting essentially of 6.7% phosphorus, 6.6% tin, 0.02% silicon, 2% nickel, and the balance copper. FIG. 7 demonstrates that a substantial color match may be achieved between sterling silver and the phos-copper alloys of the present invention. With variations in tin and nickel content, various changes in color are effected with the additions to the phos-copper brazing alloy family. This has definite advantages in decorative applications such as jewelry and other arts, where the braze alloy of the present invention is a very close color match to that of sterling silver. Previously, silver brazing alloys containing 60-75% silver were used to braze silver parts, and required the use of flux. The phos-copper base alloys of the present invention, with or without silver, may be used for brazing silver parts, and the brazing may be accomplished without the use of flux. Thus, the phos-copper alloys of the present invention offer a simpler and lower cost alternative for brazing silver.

[0048] The tables show meaningful reductions in liquidus temperatures for the Cu—P—Sn—Si and Cu—P—Sn—Ni—Si alloys of the present invention compared to the BCuP-2 alloy (alloy 1), and of the Cu—P—Ag—Sn—Ni—Si and Cu—P—Ag—Sn—Si alloys of the present invention compared to the BCuP-4 (alloy 12) and BCuP-5 (alloy 15) alloys. Further, the figures depict brazed joints using alloys of the present invention that have substantial raised shoulders or caps about the brazed joint and which are visually distinguishable from adjacent copper and copper alloys, and which are good color matches to sterling silver. The figures further show the absence of black oxide, which can obscure the operator's view of the soundness of the joint. The tables and figures further show a synergistic effect achieved with the combined additions of tin, nickel and silicon, as well as the combination of tin, nickel, silicon and silver.

[0049] While the present invention has been illustrated by the description of an embodiment thereof, and while the embodiment has been described in considerable detail, it is not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of Applicant's general inventive concept. 

What is claimed is:
 1. A solid brazing component having a liquidus temperature above 840° F. selected from the group consisting of: wire, strip, foil and preforms, wherein the brazing component is made of an alloy consisting essentially of, in weight percent: (a) about 4-10% phosphorus; (b) about 0.1-8% tin; (c) about 0.001-3% silicon; (d) up to about 3% nickel; (e) up to about 18% silver; (f) up to about 4% antimony; (g) up to about 3% manganese; and the balance copper.
 2. The component of claim 1 wherein the alloy consists essentially of: (e) about 0.1-18% silver.
 3. The component of claim 2 wherein the alloy consists essentially of: (d) about 0.1-3% nickel.
 4. The component of claim 1 wherein the alloy consists essentially of: (d) about 0.1-3% nickel.
 5. The component of claim 1 wherein the brazing component has a liquidus temperature less than about 1300° F. and a solidus temperature less than about 1200° F.
 6. The component of claim 5 wherein the alloy consists essentially of: (b) about 6-8% tin; and (d) about 1.4-2% nickel.
 7. The component of claim 6 wherein the alloy exhibits a major thermal arrest at a temperature in the range of about 1215-1240° F.
 8. The component of claim 1 wherein the alloy exhibits a major thermal arrest at a temperature in the range of about 1125-1255° F.
 9. The component of claim 1 wherein the alloy consists essentially of: (a) about 5-10% phosphorus; (b) about 0.1-6% tin; (c) about 0.001-1% silicon; (f) up to about 2% antimony; and the balance copper.
 10. The component of claim 1 wherein the alloy consists essentially of: (a) about 6-7% phosphorus; (b) about 2-8% tin; (c) about 0.001-1% silicon; (f) up to about 2% antimony; and the balance copper.
 11. The component of claim 10 wherein the alloy exhibits a major thermal arrest at a temperature below about 1275° F.
 12. The component of claim 2 wherein the alloy consists essentially of: (a) about 6% phosphorus; (b) about 6-7% tin; (c) about 0.02% silicon; (e) about 6-10% silver; (f) up to about 2% antimony; and the balance copper.
 13. The component of claim 3 wherein the alloy consists essentially of: (a) about 5-6% phosphorus; (b) about 6-7% tin; (c) about 0.02% silicon; (d) about 2% nickel; (e) about 15% silver; (f) up to about 2% antimony; and the balance copper.
 14. The component of claim 13 wherein the alloy has a liquidus temperature of about 1260° F. or less.
 15. The component of claim 2 wherein the alloy consists essentially of: (a) about 6-7% phosphorus; (b) about 2-7% tin; (c) about 0.01-0.1% silicon; (e) about 3% silver; (f) up to about 2% antimony; and the balance copper.
 16. The component of claim 4 wherein the alloy consists essentially of: (a) about 6-7% phosphorus; (b) about 6-7% tin; (c) about 0.01-0.1% silicon; (d) about 1-2% nickel; (f) up to about 2% antimony; and the balance copper, wherein the brazing component has a liquidus temperature less than about 1300° F.
 17. The component of claim 16 wherein the alloy exhibits a major thermal arrest at a temperature in the range of about 1215-1255° F.
 18. The component of claim 3 wherein the alloy consists essentially of: (a) about 4-7% phosphorus; (b) about 5-7% tin; (c) about 0.01-0.1% silicon; (d) about 1.4-2% nickel; (e) about 5-18% silver; (f) up to about 2% antimony; and the balance copper, wherein the brazing component has a liquidus temperature less than 1300° F. and a solidus temperature of about 1060° F. or less.
 19. The component of claim 18 wherein the alloy exhibits a major thermal arrest at a temperature in the range of about 1125-1160° F.
 20. The component of claim 18 wherein the alloy has a liquidus temperature in the range of about 1105-1120° F.
 21. A method of forming a brazed joint comprising the steps of: providing a solid brazing component having a liquidus temperature above 840° F. selected from the group consisting of: wire, strip, foil and preforms, wherein the brazing component is made of an alloy consisting essentially of, in weight percent: (a) about 4-10% phosphorus; (b) about 0.1-8% tin; (c) about 0.001-3% silicon; (d) up to about 3% nickel; (e) up to about 18% silver; (f) up to about 4% antimony; (g) up to about 3% manganese; and the balance copper; placing the solid brazing component between two metal parts; heating the solid brazing component to melt at least a major portion of the alloy to cause the alloy to wet and flow between the two metal parts; cooling the alloy to form a brazed joint with a raised cap between the two metal parts, wherein the brazed joint is substantially free of black metal oxide.
 22. The method of claim 21 wherein the solid brazing component is placed between two copper or copper alloy parts and the brazed joint is visually distinguishable from the parts.
 23. The method of claim 21 wherein the solid brazing component is placed between two sterling silver parts and the brazed joint is substantially the same color as the sterling silver.
 24. The method of claim 21 wherein the solid brazing component is placed between two tubular shaped parts.
 25. The method of claim 21 wherein the solid brazing component is heated to a temperature less than 1400° F. to melt the major portion.
 26. The method of claim 21 wherein the solid brazing component is heated to a temperature less than 1300° F. to melt the major portion.
 27. The method of claim 21 wherein the solid brazing component is heated to a temperature less than 1130° F. to melt the major portion. 